This invention relates to footwear such as shoes.
Some shoe designs have a cavity between the outer sole and the shoe upper which normally contains a piece of synthetic material placed in the cavity during manufacture of the shoe. Whilst providing some cushioning for the wearer, the synthetic piece does not always effectively extend throughout the outer sole such as into the heel portion of the shoe and since it is a discrete piece of material it is not possible to vary the cushioning effect in a range of shoes.
EP-A-0 018 663 describes a method of making an athletic shoe in which an upper and a preformed rubber outsole are secured together by a foamed polyurethane midsole which is injected between the two. This bonds the outsole and the upper together.
EP-A-0 048 965 discloses a padded shoe sole having orthopedic properties which consists of a wear-resistant lower walking sole layer and a flexible upper padded layer of light-weight foam. Either the walking sole layer or the upper padded layer is foam-filled in a mold and allowed to cure. The other layer is then foam-filled into the mold for curing and bonding to the first layer. The walking sole layer is bonded to the shoe upper by the upper padded layer.
U.S. Pat. No. 3,812,604 discloses a shoe which has an instep bonded to a bottom layer by an intermediate layer. The bottom layer and instep are positioned in a mold and the intermediate layer in a liquid form is flowed into the spaces between the bottom layer and the instep. The intermediate layer is cooled and bonds the bottom layer and the instep together.